instance field native JS global

<script type="text/javascript">
var a = 0;
</script>

Now I have GWT:

public class AA implements EntryPoint {

  public final int a =44;

}

How c开发者_StackOverflow社区an i transfer instance field a to native global javascript variable so that it can be callable from javascript method?

public native void init ( Integer arg )/*-{
    $wnd.a = arg;
}-*/;